This invention relates to apparatus of controlling the timings of throwing on or off cylinders of a printing press.
In a multicolor printing press it is essential to accurately print on successively supplied sheets of paper supplied from a paper feeder. For this purpose it is necessary to throw on or throw off printing cylinders and inking rollers at suitable timings commensurate with the supply of the printing paper. If the timings were not correct, sheets of paper not printed at all, or partially printed or printed with only one color would be delivered, or a printing pressure would be applied to the impression cylinder at a position where no sheet of paper is present on the printing cylinders thus spoiling the printing cylinders with printing ink.
According to prior apparatus for controlling the timings for throwing on or off the printing cylinders, a pulse shaped timing signal is generated in synchronism with the angle of rotation of the printing cylinders, and the number of the timing signals is counted by a preset counter after commencing the paper supply so that the counter produces an output signal when a preset number of the timing signals is counted and the printing cylinders are thrown on or thrown off with the output signal. With this apparatus, it is necessary to provide preset counters of the number equal to that of the printing cylinders or inking rollers to be controlled so that in a multicolor printing press it is necessary to provide a large number of the preset counters.
Furthermore, with the control apparatus described above, since the accuracy of timing is determined in accordance with the spacing or interval between the timing pulses, in order to improve the control accuracy it is necessary to increase the number of the timing pulses outputted per one revolution of the printing cylinders or during a printing time for each sheet of paper. As the number of the pulses increases in this manner, it is necessary to use a preset counter having a high response speed. Moreover, in the multicolor printing press, as the number of the steps of printing increases it is necessary to count a larger number of pulses, thus requiring to use a preset counter having larger number of stages. In other words, as it is necessary to use many expensive preset counters, the cost of the apparatus increases. Since highly sensitive preset counters are used, even a small noise causes misoperation of the counter.